OK, here goes my two cents on my KX3 operation. I use the internal speaker for CW only. I use a miniX self powered speaker for quiet portable work and I use a FM modulator from the phone jack while in the mobile to the car FM receiver. All seems to work fine. This way I don't worry about impedance issues.
Mel, K6KBE From: Don Wilhelm <donw...@embarqmail.com> To: w7aqk <w7...@cox.net>; Elecraft Reflector <elecraft@mailman.qth.net> Sent: Monday, January 23, 2017 1:35 PM Subject: Re: [Elecraft] Audio Output Impedance of the KX3 David, Let me try to respond and perhaps Jim will chime in a well. Modern audio amplifier output stages are very low output impedance devices. As such, they can produce as much power as the device connected will allow. In a practical design of course there is a limit to how much current the attached device (speaker or headphones) can draw from the amplifier. With that being said, the lower the impedance, the more current that will be drawn. Speakers are generally in the 4 ohm to 8 ohm region and a 4 ohm speaker will draw more current and develop more power than an 8 ohm speaker. The efficiency of a speaker makes a big difference in the amount of sound it produces. Headphones are a slightly different matter (but only slightly) in that they are typically higher impedance and the current will be lower, and the voltage across it can be higher, but they are more efficient than speakers so it usually does not matter. The efficiency of headphones is usually expressed in SPL - the higher the number, the greater the sensitivity. Impedance does not matter much except in some low efficiency Hi-Fi audiophile headphones. In an analogy, consider the AC power line - that is a very low impedance source of a fixed voltage. How much power is taken from the line depends on the impedance of the device plugged into it. Within limits, an audio amplifier shares some of the same characteristics even though its voltage and power are much more limited. 73, Don W3FPR On 1/23/2017 3:06 PM, w7aqk wrote: > Jim, > > Maybe you could expand on that somewhat as I'm still confused a bit. > Perhaps I'm not understanding what I hear, or why, but it almost always > seems that when speakers (or headphones) are not closely matched to the > designed impedance I notice some deterioration in output. Some mismatch > doesn't seem too serious, but when the difference is high, it seems much > more noticeable. > > On the other hand, I've also experienced that using headphones with > higher sensitivity ratings (like most Sony ear buds) tends to provide > much higher output. Most ear buds tend to be 32 ohm (16 at lest), but I > find Sony ear buds usually work best as many of them have sensitivity > ratings up around -108 dbm. I could very well be fooling myself! > > This topic was covered somewhat similarly back when folks, including me, > were complaining about poor audio output from Heil headphones. The > headphone portion of my Yamaha CM500 works a lot better than my Heil, > but neither works as well as some ear buds. I don't really have another > good pair of headphones around here to try. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to farrerfo...@yahoo.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com